In order to allow advanced control of a lighting system, devices and methods have been developed where the light output of each light source is modulated by a modulation signal. The modulation signal comprises individual information, such as an identification code or data regarding light source properties, etc. By thus providing each light output signal with such individual information it is possible to for instance remotely check the status of the light sources, or to facilitate the identifying of the contribution from each light source to an overall light output that is remotely detected, i.e. detected at a distance from the light sources.
One such lighting system that is known in the prior art is disclosed in WO 2006/111927, where the light intensity of different light sources is individually controlled. The lighting system comprises a plurality of light sources, a detector device, and a master controller. Each light source is driven by a drive signal, which comprises a power signal, and a modulation signal, which modulates the power signal. The modulation signal carries the information content, while the power signal provides the basic power that determines the light intensity of the light source. The overall light output is remotely detected, by means of the detector device, and the individual contributions from the respective light sources are identified by means of individual modulation signals, which comprise identification information. Further, each modulation signal comprises additional data, such as status information, about the associated light source. A light property, such as intensity, of each light source is estimated. The information thus obtained is sent to the master controller, which determines any necessary adjustments of the light outputs of the light sources. Adjustment data is sent to the drive devices of the light sources for adjusting said power signals.
The known control method and control device of WO2006/111927, as well as other similar methods and devices, are independent of the actual configuration of the lighting system. They are not optimum for a given setup of different light sources. Typically, different light sources have a different distance to the detector, have a different light intensity, and have a different orientation with respect to the detector. Still it is desired to achieve a high reliability in detection of the individual information as well as the light property, even for a large number of light sources. In the prior art concepts this would only be possible by designing for the light source with the worst case performance. That inherently decreases the dimming range, i.e. the range between the lowest possible and the highest possible intensity of the light output, and data rate of the lighting system to an unnecessarily high extent. It should be noted that the dimming range is affected by the power that is used by the very modulation signal.